The United Kingdom recorded more than 230,000 deaths from COVID-19, a similar death rate to the United States and Italy but higher than elsewhere in western Europe, and it is still recovering from the economic consequences.
An inquiry, which Johnson ordered in May 2021, delivered a blistering assessment of his government's response to COVID-19, criticising his indecisive leadership, lambasting his Downing Street office for breaking their own rules and castigating his top adviser Dominic Cummings.
"There was a toxic and chaotic culture at the centre of the UK government during the pandemic," the inquiry chair, former judge Heather Hallett, said in her report.
"I can summarise my findings of the response as too little too late," Hallett said on Thursday.
"All four governments failed to appreciate the scale of the threat or the urgency of response it demanded in the early part of 2020, relying in part on misleading assurances that the UK was properly prepared for a pandemic."
Hallett said Johnson had failed to appreciate the seriousness of the virus after it emerged, believing it would amount to nothing and was distracted by other government business, with the UK at the time bogged down in talks over its departure from the European Union.
"Mr Johnson should have appreciated sooner that this was an emergency that required prime ministerial leadership to inject urgency into the response," the report said.
When he appeared before the committee in 2023, Johnson said his government had been too complacent and had "vastly underestimated" the risks, saying he understood the public's anger.
Hallett said by the time Johnson announced a lockdown on March 23 it was too little, too late, a repeated criticism she levelled at the UK government and the devolved administrations of Scotland, Wales and Northern Ireland.
Had the UK locked down just a week earlier on March 16, as the consensus of evidence said it should, the number of deaths in the first wave up to July would have been reduced by about 23,000 or 48 per cent, the report concluded.
A failure to act sooner again as cases rose later in the year also led to further lockdowns, it added.
But Hallett added the "inquiry does not advocate for national lockdowns - far from it".
"Restricting people's liberty in such a draconian fashion with all the devastating consequences should be avoided, if at all possible.
"But to avoid them, governments must take timely and decisive action to control a spreading virus. The four governments of the UK did not."
The inquiry's report said government cabinet members including health secretary Matt Hancock plus key scientists all failed to act with the urgency needed to tackle the virus.
And she said Johnson's special adviser Cummings used "offensive, sexualised and misogynistic" language as he "poisoned" the atmosphere in Downing Street.
Hallett said the inquiry recognised Johnson had to wrestle with profound decisions but said he repeatedly changed his mind, failing to make timely decisions despite a clearer understanding of the virus.
with DPA, AP and PA
